1. Field of the Invention
The present invention relates to a heat bonding method and a heat bonding device for bonding a first component part and a second component part. Still more particularly, the invention relates to a preferred heat bonding method and a preferred heat bonding device for performing a heat bonding between outer leads of electronic parts such as tape carrier package and electrodes formed on a substrate such as a display panel.
2. Description of the Related Art
A plurality of electronic parts are mounted, as drivers for a display panel, on electrodes which are formed, with a narrow pitch, on peripheral sections of the display panel which will be used as a display device for electronic devices.
FIGS. 6A and 6B are diagrams explaining a conventional heat bonding method for outer leads of electronic parts. In particularly, FIG. 6A shows a state before the heat bonding and FIG. 6B shows a state after the heat bonding.
An electronic part 51 is formed by bonding to a bare chip 53 a film carrier 52 made of a polyimide resin and others. On a surface of the film carrier 52, a plurality of outer leads 54 made of copper, etc. are formed with a narrow pitch.
In the peripheral sections of a transparent plate 56, a plurality of microelectrodes 58 are formed with a narrow pitch. At both ends of the film carrier 52, first and second marks MA and MB for position detection are formed with a predetermined distance. On the other hand, at both the ends of the string of the microelectrodes 58 formed on the transparent plate 56, first and second marks NA and NB are formed, which correspond to the first and second marks MA and MB. Both the marks MA and NA and both the marks NB and NB are used as pair, respectively.
At first, in the state before performing the heat bonding shown in FIG. 6A, a difference in position between the first marks MA and NA is detected, and a difference in position between the second marks MB and NB by using a camera (not shown) is detected.
Next, the outer leads 54 and the microelectrodes 58 are positioned so that the difference between the pair of the first marks MA and NA becomes equal to the difference between the pair of the second marks MB and NB. Then, a bonding member (not shown) is pressed to the film carrier 52 in order to perform the heat bonding between the outer leads 54 and the corresponding microelectrodes 58 (see FIG. 6B). The outer leads 54 are thereby bounded to the corresponding microelectrodes 58 by the heat bonding, so that the electronic part 51 is mounted on the transparent plate 56 of the display panel.
Because the outer leads 54 are formed with a narrow pitch on the surface of the film carrier 52, it is necessary to perform the heat bonding after the completion of accurate positioning between the outer leads 54 and the microelectrodes 58 of the display panel.
However, because the film carrier 52 is made of a polyimide resin and others, the film carrier 52 is expanded during the heat bonding. In an actual case, the film carrier 52 is formed shorter in length in consideration of its expansion during the heat bonding. Because a manufacturing error occurs, even if the heat bonding is performed under a same condition, there happens that it is difficult to bond the outer leads 54 to the corresponding microelectrodes 58 in accurate position, so that faulty products are manufactured. In the related art, the condition of the heat bonding is reviewed every occurring faulty product. In the future, it can be predicted that narrowing a pitch will cause the increasing of the number of faulty products.
In order to avoid the drawback of the related art described above, a method to suppress the rate of faulty products has been proposed. In this method, the state of the heat bonding is observed, and the condition of the heat bonding that will be performed in a following process is reviewed as necessary based on data obtained by this observation.
However, a manufacturing error in a film carrier after the completion of the heat bonding is not always equal to a manufacturing error involved in a film carrier before the performing of the heat bonding. Thereby, there is a drawback that a condition for the heat bonding determined based on the data obtained from a film carrier to which the heat bonding has been performed can not be applied to following film carriers.
An aspect of the present invention provides a heat bonding method and a heat bonding device capable of suppressing an incidence of faulty products even if manufacturing errors in component parts are not always equal to each other.
In a heat bonding method and a heat bonding device according to an embodiment of the present invention, the heat bonding between first and second component parts is performed, wherein an expansion amount of the first component part is changed according to a condition of the heat bonding. First and second marks formed on the first component part is detected before performing the heat bonding. A distance between the first and second marks detected is then obtained. An optimum condition for the heat bonding is determined based on the distance obtained. The heat bonding is performed for the first and second component parts under the optimum condition determined above.